Heretofore, intrinsic losses in optical fibers have called for the use of complicated electro-optic and/or opto-electronic repeaters to amplify the optical signals in long-haul communications links (usually those greater than approximately 70 kilometers in length). Repeaterless links are more desirable, however, since they are less expensive and help assure more reliable systems. Cost and reliability become even more important factors in the realm of undersea communications, since repeaterless links relieve the initial expense of the repeaters, but also the recovery and servicing expenses associated with the optical repeaters.
Thus a continuing need exists in the state of the art for a long-haul communications link not requiring interspersed repeaters, yet which will provide meaningful data at usable signal levels at a receiving station.